The present invention relates to an optical pickup device for emitting and/or receiving a light beam to read out a signal from an optical recording medium and/or record the signal on the optical recording medium, and an optical disk driver for driving an optical recording disk while reading out the signal from the optical recording disk and/or recording the signal on the optical recording disk.
A prior art optical pickup device as disclosed by JP-A-10-154344 contains two light beam sources respectively generating light beams whose wave lengths are different from each other.
An object of the present invention is to provide an optical pickup device for emitting at least two laser beams whose wave lengths are different from each other to be suitable for respective optical recording mediums either of which optical recording mediums is selectively operated on an optical disk driver so that a signal is read out from and/or recorded onto the selected one of the optical recording mediums, by which optical pickup device energies of the laser beams generated by respective laser beam sources are effectively utilized to read out the signal from and/or record the signal onto the optical recording mediums while a cross sectional shape (along an imaginary plane perpendicular to an optical axis of laser beam) of at least one of the laser beam is adjusted to become preferable for extremely-high recording density recording medium.
According to the present invention, an optical pickup device for emitting at least two laser beams whose wave lengths are different from each other to be suitable for respective optical recording mediums either of which optical recording mediums is selectively operated on an optical disk driver so that a signal is read out from and/or recorded onto the selected one of the optical recording mediums, includes a light beam source for generating the laser beams, an objective lens for focusing the laser beams on respective recording surfaces of the optical recording mediums, an upstream common optical path for passing along a common optical axis thereof the laser beams from the light beam source, a downstream common optical path for passing along a common optical axis thereof the laser beams toward the objective lens, a pair of divergence point and confluence point between the upstream and downstream common optical paths, at which divergence point the laser beams from the upstream common optical path diverge from each other, and at which confluence point the laser beams converge into the downstream common optical path, and an anamorphic system arranged between the divergence point and confluence point along one of the laser beam to change a cross-sectional shape of the one of the laser beams from an oval toward a circle.
Since the anamorphic system is arranged to change the cross-sectional shape of the one of the laser beams from the oval toward the circle between the divergence point and the confluence point along the one of the laser beam between the upstream common optical paths of the laser beams from the light beam source and the down upstream common optical paths of the laser beams toward the objective lens, at which divergence point the laser beams from the upstream common optical path diverge from each other, and at which confluence point the laser beams converge into the downstream common optical path, the cross sectional shape (along an imaginary plane perpendicular to an optical axis of laser beam) of the one of the laser beam is adjusted to become preferable for extremely-high recording density recording medium while an optical energy of another one of the laser beam is prevented from being absorbed by the anamorphic system.
If the divergence point and confluence point are prevented from being separated away from each other so that the one of the laser beams proceeds from the divergence point to the confluence point to form a closed loop on which the anamorphic system is arranged, the optical energy of the another one of the laser beam is prevented from being absorbed between the divergence point and confluence point. If the divergence point and confluence point are separated away from each other so that the one of the laser beams and the another of the laser beams proceed in parallel from the divergence point to the confluence point, an angular relationship between the upstream and downstream common optical paths can be freely set. It is preferable for effectively utilizing the optical energy of the another one of the laser beams that the anamorphic system for changing the cross-sectional shape of the one of the laser beams is prevented from changing a cross-sectional shape of another one of the laser beams.
If the divergence point includes a wavelength selective element for separating the laser beams away from each other on the basis of a difference in wavelength between the laser beams, an optical energy loss on separating the laser beams from each other between the divergence point and confluence point is minimized. It is preferable that the wavelength selective element is a wavelength selective mirror. If the wavelength selective mirror allows the one of the laser beams to be transmitted through the wavelength selective mirror so that the one of the laser beams is introduced to the anamorphic system, the one of the laser beams after passing the anamorphic system can be transmitted through the wavelength selective mirror at the divergence point to converge at the confluence point into the downstream common optical path with the another one of the laser beams, so that the one of the laser beams and the another one of the laser beams can diverge from each other and converge with each other at the same or identical point of the divergence point and confluence point prevented from being separated from each other when the single wavelength selective mirror operates as both the divergence point and confluence point for separating the laser beams from each other and converging the laser beams into the downstream common optical path.
The optical pickup device may further comprise a collimator on the upstream common optical path to convert non-parallel rays of each of the laser beams to parallel rays thereof.
The confluence point may include a wavelength selective mirror for allowing the laser beams to be introduced to the downstream common optical path, so that an optical energy loss on converging the laser beams into the downstream common optical path is minimized. The wavelength selective mirror may allow the one of the laser beams to be transmitted through the wavelength selective mirror so that the one of the laser beams from the anamorphic system is introduced to the downstream common optical path.
The device may include a one-piece optical element on which the pair of divergence point and confluence point and the anamorphic system are formed so that the one of the laser beams is prevented from passing through a gaseous atmosphere between the divergence point and the confluence point. The device may include a one-piece optical element on which the divergence point and the confluence point are formed at the same position so that another one of the laser beams is prevented from passing through a gaseous atmosphere between the divergence point and the confluence point, so that an optical energy loss and a cross sectional shape change of the another one of the laser beams are prevented between the divergence point and the confluence point.
If the device includes a single wavelength selective mirror performable as both the divergence point and the confluence point, an optical energy loss of the laser beams is restrained between the divergence point and the confluence point.
The divergence point may be exposed to a gaseous atmosphere through which the laser beams reach the divergence point. An optically transparent element may covers the divergence point so that the laser beams are allowed to reach the divergence point through the optically transparent element. If a surface of the transparent element for receiving the laser beams toward the divergence point thereon is prevented from extending perpendicularly to the laser beams proceeding into the transparent element from the light beam source, the laser beams are restrained from being reflected by the divergence point and the surface of the transparent element toward the collimator and the light beam source.
When the device has an anamorphic element on which the anamorphic system is formed, it is preferable for forming the anamorphic system that a surface of the anamorphic element for receiving the one of the laser beam to form the anamorphic system is exposed to a gaseous atmosphere so that the one of the laser beam reaches the surface of the anamorphic element through the gaseous atmosphere. If an angle between the one of the laser beam to be taken into the anamorphic element and a direction perpendicular to the surface of the anamorphic element is larger than an angle between the one of the laser beam to be returned to the surface of the anamorphic element and the direction perpendicular to the surface of the anamorphic element, the cross sectional shape of the one of the laser beams after adjusted by the anamorphic system is restrained from deteriorated when the one of the laser beams proceeds out of the anamorphic element. When the one of the laser beam proceeds through a gaseous atmosphere between the anamorphic system and each of the divergence point and the confluence point, a positional relationship amoung the anamorphic system, the divergence point and the confluence point is adjusted easily.